In the field of total shoulder prostheses, prostheses are commonly said to be inverted when they comprise a glenoid component that is integral with the glenoid surface of a scapula of a patient's shoulder and that delimits a convex articular surface and a humeral component that is integral with the humerus of the patient's shoulder and that delimits a concave articular surface. The cooperation of the articular surfaces of the glenoid and humeral components allow an articulated connection to be reproduced at the shoulder. However, it is common with this type of prosthesis that during adductive movement of the shoulder, the lower portion of the humeral prosthetic component strikes the pillar of the scapula, i.e. the lower portion of the glenoid located just below the glenoid prosthetic component (when the patient is standing upright). This interference between the humeral prosthetic component and the scapula limits the range of adductive movement of the shoulder and may cause pain to the patient or even lead to the prosthesis becoming dislodged due to, for example, osteolysis of the scapula.
Another method used to replace damaged shoulder joints is interpositional arthroplasty. The method of interpositional arthroplasty uses tissue from the patient or an artificial replacement to repair a damaged or malformed joint. An interpositional implant is positioned at the joint to act as an engagement surface between two adjacent bone structures to allow articular movement. In the particular field of interpositional shoulder arthroplasty, the humeral metaphysis is typically impacted to form an engagement surface for an interpositional implant positioned between a glenoid component (or glenoid) and a humeral component (or humeral metaphysis). However, if the cancellous bone in the humeral metaphysis is of poor or degraded quality, the cancellous bone may lead to gradual subsidence of the interpositional implant within the humeral metaphysis. It is thus desirable to develop an interpositional implant with a metaphyseal articular surface that will provide support and protection to the metaphyseal cancellous bone.